[PATCH] daemon: support listening on Unix domain sockets

[Eric Wong <e@80x24.org>]

Listening on Unix domain sockets can be convenient for running
behind reverse proxies, avoiding port conflicts, limiting access,
or avoiding the overhead (if any) of TCP over loopback.
---
 lib/PublicInbox/Daemon.pm | 43 +++++++++++++++++++++++++++----------------
 t/httpd-corner.t          | 25 +++++++++++++++++++++++--
 2 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index c101ecb..6caa1d3 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -7,6 +7,7 @@ use strict;
 use warnings;
 use Getopt::Long qw/:config gnu_getopt no_ignore_case auto_abbrev/;
 use IO::Handle;
+use IO::Socket;
 STDOUT->autoflush(1);
 STDERR->autoflush(1);
 require Danga::Socket;
@@ -52,13 +53,18 @@ sub daemon_prepare ($) {
 
 	foreach my $l (@cfg_listen) {
 		next if $listener_names{$l}; # already inherited
-		require IO::Socket::INET6; # works for IPv4, too
-		my %o = (
-			LocalAddr => $l,
-			ReuseAddr => 1,
-			Proto => 'tcp',
-		);
-		if (my $s = IO::Socket::INET6->new(%o)) {
+		my (%o, $sock_pkg);
+		if (index($l, '/') == 0) {
+			$sock_pkg = 'IO::Socket::UNIX';
+			%o = (Type => SOCK_STREAM, Local => $l);
+		} else {
+			$sock_pkg = 'IO::Socket::INET6'; # works for IPv4, too
+			%o = (LocalAddr => $l, ReuseAddr => 1, Proto => 'tcp');
+		}
+		eval "use $sock_pkg";
+		die $@ if $@;
+		$o{Listen} = 1024;
+		if (my $s = $sock_pkg->new(%o)) {
 			$listener_names{sockname($s)} = $s;
 			push @listeners, $s;
 		} else {
@@ -165,15 +171,20 @@ sub sockname ($) {
 sub host_with_port ($) {
 	my ($addr) = @_;
 	my ($port, $host);
-	if (length($addr) >= 28) {
-		require Socket6;
-		($port, $host) = Socket6::unpack_sockaddr_in6($addr);
-		$host = '['.Socket6::inet_ntop(Socket6::AF_INET6(), $host).']';
-	} else {
-		($port, $host) = Socket::sockaddr_in($addr);
-		$host = Socket::inet_ntoa($host);
-	}
-	($host, $port);
+
+	# this eval will die on Unix sockets:
+	eval {
+		if (length($addr) >= 28) {
+			require Socket6;
+			($port, $host) = Socket6::unpack_sockaddr_in6($addr);
+			$host = Socket6::inet_ntop(Socket6::AF_INET6(), $host);
+			$host = "[$host]";
+		} else {
+			($port, $host) = Socket::sockaddr_in($addr);
+			$host = Socket::inet_ntoa($host);
+		}
+	};
+	$@ ? ('127.0.0.1', 0) : ($host, $port);
 }
 
 sub inherit () {
diff --git a/t/httpd-corner.t b/t/httpd-corner.t
index 198a7e9..0338c8a 100644
--- a/t/httpd-corner.t
+++ b/t/httpd-corner.t
@@ -16,6 +16,7 @@ use Digest::SHA qw(sha1_hex);
 use File::Temp qw/tempdir/;
 use Cwd qw/getcwd/;
 use IO::Socket;
+use IO::Socket::UNIX;
 use Fcntl qw(FD_CLOEXEC F_SETFD F_GETFD :seek);
 use Socket qw(SO_KEEPALIVE IPPROTO_TCP TCP_NODELAY);
 use POSIX qw(dup2 mkfifo :sys_wait_h);
@@ -34,20 +35,30 @@ my %opts = (
 	Listen => 1024,
 );
 my $sock = IO::Socket::INET->new(%opts);
+my $upath = "$tmpdir/s";
+my $unix = IO::Socket::UNIX->new(
+	Listen => 1024,
+	Type => SOCK_STREAM,
+	Local => $upath
+);
+ok($unix, 'UNIX socket created');
 my $pid;
 END { kill 'TERM', $pid if defined $pid };
 my $spawn_httpd = sub {
 	my (@args) = @_;
+	$! = 0;
 	my $fl = fcntl($sock, F_GETFD, 0);
 	ok(! $!, 'no error from fcntl(F_GETFD)');
 	is($fl, FD_CLOEXEC, 'cloexec set by default (Perl behavior)');
 	$pid = fork;
 	if ($pid == 0) {
 		# pretend to be systemd
-		fcntl($sock, F_SETFD, $fl &= ~FD_CLOEXEC);
 		dup2(fileno($sock), 3) or die "dup2 failed: $!\n";
+		dup2(fileno($unix), 4) or die "dup2 failed: $!\n";
+		IO::Handle->new_from_fd(3, 'r')->fcntl(F_SETFD, 0);
+		IO::Handle->new_from_fd(4, 'r')->fcntl(F_SETFD, 0);
 		$ENV{LISTEN_PID} = $$;
-		$ENV{LISTEN_FDS} = 1;
+		$ENV{LISTEN_FDS} = 2;
 		exec $httpd, @args, "--stdout=$out", "--stderr=$err", $psgi;
 		die "FAIL: $!\n";
 	}
@@ -63,6 +74,16 @@ my $spawn_httpd = sub {
 	$spawn_httpd->('-W0');
 }
 
+# Unix domain sockets
+{
+	my $u = IO::Socket::UNIX->new(Type => SOCK_STREAM, Peer => $upath);
+	ok($u, 'unix socket connected');
+	$u->write("GET /host-port HTTP/1.0\r\n\r\n");
+	$u->read(my $buf, 4096);
+	like($buf, qr!\r\n\r\n127\.0\.0\.1:0\z!,
+		'set REMOTE_ADDR for Unix socket');
+}
+
 sub conn_for {
 	my ($sock, $msg) = @_;
 	my $conn = IO::Socket::INET->new(
-- 
EW